'It was not like the flu or anything else I’ve had before'

As states begin to reopen and public health officials begin planning for the fall and the beginning of flu season, scientists are learning more about how COVID-19 both resembles and is more dangerous than the more well-known seasonal influenza.

“Both viruses attach to the cells of airways and can get in and do quite a bit of damage,” said Dr. Craig M. Lilly, critical care specialist at UMass Memorial Health Care. “The major clinical differences is that this particular coronavirus is novel. That is, no human had been exposed to this or a similar virus as far as we know in human history.”

In other words, although some of the symptoms can be similar -- fever, cough, body aches and fatigue –there is one major difference: We don’t yet know how to fight COVID-19.

Because the flu has been around for centuries, there are tools that keep death rates at a minimum: vaccines, antivirals, and even human immunity have been developed in response to flu pandemics over time.

The lack of resources to fight COVID-19 is reflected in the number of deaths reported. As of May 19, there have been more than 90,000 coronavirus deaths in the United States in the 16 weeks since it hit the country in January, while the flu causes an average of 12,000 to 62,000 deaths in the U.S. in its 30-week season each year.

Comparing the mortality rates of the viruses is complicated given the number of contributing factors, like access to quality health care. But so far, data show the mortality of COVID-19 is about 10 times higher than the rate for season flu, which is usually approximately 0.1%.

Although COVID-19 and the flu can both be transmitted through droplets from coughing, sneezing or talking, doctors believe the coronavirus may also be spread through airborne infection. This means droplets may hang in the air and infect someone even after the infected person leaves the area. On average, someone with COVID-19 will infect more people than someone with influenza.

The virus is insidious, and difficult to detect without testing in many, meaning asymptomatic patients can spread it unwittingly, said Dr. Jamie Colbert, hospitalist at Newton Wellesley Hospital and a senior medical director at Blue Cross.

"About 25%-40% of cases of COVID-19 infections are in patients with no or very mild symptoms," he said. "This is a big difference from influenza and contributes to the transmission of the disease."

And symptoms set in later even for those who develop them, contributing to the virus' easy spread.

"COVID-19 seems to have a longer incubation period -- usually 4-7 days from exposure to symptom onset -- compared to 2-3 days for influenza," Colbert said. "This gives someone exposed to COVID more time to spread virus before they know they are ill and can quarantine."

COVID-19 also appears to result in a higher rate of severe cases than the flu. The World Health Organization reports that data suggests 80% of coronavirus infections are mild or asymptomatic, 15% are severe infection requiring oxygen and 5% are critical infections, requiring ventilation. The flu, by contrast, results in severe cases in about .4% of patients.

There is also an alarmingly rapid decline seen in some COVID-19 patients, Lilly said, far more sudden than in flu patients.

Casey Henshaw, a 25-year-old from Gainesville, Florida, knows first-hand how quickly COVID-19 can go from mild to serious.

What started as a sore throat on March 19 quickly turned into intense pain in her chest and back. She had pneumonia in both lungs, requiring a three-day hospital stay.

She had never experienced such a rapid downturn – and never before had the inability to catch her breath.

Thankfully, Henshaw had a successful recovery. But she stressed the importance of contacting a doctor if symptoms arise.

“Hopefully if you are infected it is no worse than the flu, but it could be much, much worse,” she said.

It is unknown if being infected with COVID-19 now will mean immunity in the future.

"Influenza has many different subtypes and the seasonal flu each year is slightly different. This means that infection with flu one year does not necessarily protect against infection in subsequent years," Colbert noted. "As COVID-19 is novel, we don’t yet know if infection now will protect one from future infection."

Although there is no prevention or treatment for COVID-19, researchers around the world are working to develop medications and vaccines. Several therapeutics are in clinical trials in China and at least 70 potential vaccines are in progress across the U.K., U.S. and China.

Dr. Anthony Fauci, the head of the National Institute of Allergy and Infectious Diseases, has estimated a vaccine will be available within 12-18 months. The Food and Drug Administration is working with researchers to find the quickest path to discovery and implementation, shortening trial times and increasing communication between the government and scientists.

^{PHOTO OF DR. JAMIE COLBERT BY MICHAEL GRIMMETT}